JezK
Edit File: pysqlcipher.py
# dialects/sqlite/pysqlcipher.py # Copyright (C) 2005-2024 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: https://www.opensource.org/licenses/mit-license.php """ .. dialect:: sqlite+pysqlcipher :name: pysqlcipher :dbapi: sqlcipher 3 or pysqlcipher :connectstring: sqlite+pysqlcipher://:passphrase@/file_path[?kdf_iter=<iter>] Dialect for support of DBAPIs that make use of the `SQLCipher <https://www.zetetic.net/sqlcipher>`_ backend. Driver ------ Current dialect selection logic is: * If the :paramref:`_sa.create_engine.module` parameter supplies a DBAPI module, that module is used. * Otherwise for Python 3, choose https://pypi.org/project/sqlcipher3/ * If not available, fall back to https://pypi.org/project/pysqlcipher3/ * For Python 2, https://pypi.org/project/pysqlcipher/ is used. .. warning:: The ``pysqlcipher3`` and ``pysqlcipher`` DBAPI drivers are no longer maintained; the ``sqlcipher3`` driver as of this writing appears to be current. For future compatibility, any pysqlcipher-compatible DBAPI may be used as follows:: import sqlcipher_compatible_driver from sqlalchemy import create_engine e = create_engine( "sqlite+pysqlcipher://:password@/dbname.db", module=sqlcipher_compatible_driver ) These drivers make use of the SQLCipher engine. This system essentially introduces new PRAGMA commands to SQLite which allows the setting of a passphrase and other encryption parameters, allowing the database file to be encrypted. Connect Strings --------------- The format of the connect string is in every way the same as that of the :mod:`~sqlalchemy.dialects.sqlite.pysqlite` driver, except that the "password" field is now accepted, which should contain a passphrase:: e = create_engine('sqlite+pysqlcipher://:testing@/foo.db') For an absolute file path, two leading slashes should be used for the database name:: e = create_engine('sqlite+pysqlcipher://:testing@//path/to/foo.db') A selection of additional encryption-related pragmas supported by SQLCipher as documented at https://www.zetetic.net/sqlcipher/sqlcipher-api/ can be passed in the query string, and will result in that PRAGMA being called for each new connection. Currently, ``cipher``, ``kdf_iter`` ``cipher_page_size`` and ``cipher_use_hmac`` are supported:: e = create_engine('sqlite+pysqlcipher://:testing@/foo.db?cipher=aes-256-cfb&kdf_iter=64000') .. warning:: Previous versions of sqlalchemy did not take into consideration the encryption-related pragmas passed in the url string, that were silently ignored. This may cause errors when opening files saved by a previous sqlalchemy version if the encryption options do not match. Pooling Behavior ---------------- The driver makes a change to the default pool behavior of pysqlite as described in :ref:`pysqlite_threading_pooling`. The pysqlcipher driver has been observed to be significantly slower on connection than the pysqlite driver, most likely due to the encryption overhead, so the dialect here defaults to using the :class:`.SingletonThreadPool` implementation, instead of the :class:`.NullPool` pool used by pysqlite. As always, the pool implementation is entirely configurable using the :paramref:`_sa.create_engine.poolclass` parameter; the :class:`. StaticPool` may be more feasible for single-threaded use, or :class:`.NullPool` may be used to prevent unencrypted connections from being held open for long periods of time, at the expense of slower startup time for new connections. """ # noqa from __future__ import absolute_import from .pysqlite import SQLiteDialect_pysqlite from ... import pool from ... import util class SQLiteDialect_pysqlcipher(SQLiteDialect_pysqlite): driver = "pysqlcipher" supports_statement_cache = True pragmas = ("kdf_iter", "cipher", "cipher_page_size", "cipher_use_hmac") @classmethod def dbapi(cls): if util.py3k: try: import sqlcipher3 as sqlcipher except ImportError: pass else: return sqlcipher from pysqlcipher3 import dbapi2 as sqlcipher else: from pysqlcipher import dbapi2 as sqlcipher return sqlcipher @classmethod def get_pool_class(cls, url): return pool.SingletonThreadPool def on_connect_url(self, url): super_on_connect = super( SQLiteDialect_pysqlcipher, self ).on_connect_url(url) # pull the info we need from the URL early. Even though URL # is immutable, we don't want any in-place changes to the URL # to affect things passphrase = url.password or "" url_query = dict(url.query) def on_connect(conn): cursor = conn.cursor() cursor.execute('pragma key="%s"' % passphrase) for prag in self.pragmas: value = url_query.get(prag, None) if value is not None: cursor.execute('pragma %s="%s"' % (prag, value)) cursor.close() if super_on_connect: super_on_connect(conn) return on_connect def create_connect_args(self, url): plain_url = url._replace(password=None) plain_url = plain_url.difference_update_query(self.pragmas) return super(SQLiteDialect_pysqlcipher, self).create_connect_args( plain_url ) dialect = SQLiteDialect_pysqlcipher